Indirectly heated cathode assembly for magnetron



Dec. 8, 1959 v. UPSHAW ETAL 2,916,651

INDIRECTLY HEATED CATHODE ASSEMBLY FOR MAGNETRON Filed June 11, 1959 Fig.

1A! '1 q 37 q 4 I E Q 3 3e 26 1 I 35 III II II United States Patent "ice v I 2,916,651 1 I INDIRECTLY HEATED CATHODE ASSEMBLY F0 7 a v MAGNETRON Vert Upshaw and Daniel L.'Moriarty, Jr., Elmira, N.Y.,

' assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application June 11, 1959, Serial No. s'19,192

' 4 Claims. (Cl. 313-337) 2,916,651 Patented Dec. 8, 1959 between a shoulder 36' on the guide support and the lower end of ceramic sleeve 33. The heat dissipators 30 and 31 are provided respectively with extended curved edges '37 and 38 to provide substantial or increased surface area.

A tubular conductor lead 40 extends through the central aperture in end wall 14 and heat dissipator 31 and is in contact with the plate '23, which'is fixed to the heating filament '20, and a rod conductor 42 is disposed axially of the tubular conductor 41 and is fixed to plate 24 by screw means 42 which in turn receives the other leg 22 of the heating filament. The'rod and tube are main tained out of physical contact with each other by some suitable arrangement in order to prevent short circuiting when current is supplied to the heating filament 20.

From the above detailed description it will be apparent that the only insulating or descructible material used in I the cathode assembly is the ceramic sleeve 60, all other a cathode assembly of the indirectly heated type which permits continuous use over extended periods at high temperatures.

Another object is to mount the heating element within the cathode structure in a manner to prevent or reduce damage to the cathode structure.

These and other objects of the invention will hereinafter become more fully apparent from the following description of the annexed drawings, wherein:

Fig. 1 is a sectional view of a cathode assembly showing details of the invention;

Figs. 2 and 3 are sectional views taken on the lin 22 and 33 respectively of Fig. 1.

In Fig. l, the cathode assembly 110 comprises a cylinder or sleeve 11 made of any suitable refractory material, such as molybdenum, and has an electron-emissive thoria coating 12 thereon. The cylinder '11 is provided with centrally apertured end walls 13 and 14 preferably of molybdenum and the end walls are respectively provided with inwardly extending flanges 15 and 16 to frictionally receive and hold the ends of the cylinder 12 and provide a compartment 17. A filament or heating element 20, which is constructed of a single-strand non-inductive tungsten wire formed into a reverse or double helix, is enclosed within the compartment 17. The heating element '20 is supported in a manner to prevent its physical contact with the walls of the cylinder and terminates as shown in the lower portion of Fig. 1 in spaced legs 21 and 22 and is bent at its other end to provide the reverse or.

double helix. As shown in Figs. 1 and 2, the legs 21 and 22 are respectively attached to plates Q3 and 24, the plate 24 being spaced from the end wall 14 while the plate Q13 abuts the inner face of the end Wall 14 and is secured thereto by screw means 25 in Fig. 2. As shown in .Fig. 3 a crossover connection 26 is provided at the other end of the filament when the reverse helix is formed and functions as will be mentioned later.

Similar heat dissipators '30 and 31 are mounted exteriorly of the end walls 13 and 14 respectively and each is provided with a central aperture which is aligned with the aper e in its r pec iv nd pla e. A nn .2 is provided as shown at one end of the cylinder '11 and extends through the aperture n e d Wall &3 a d dissipator 30. The bonnet 32 receives a ceramic sleeve or bushing 6-3 in sliding engagement and the sleeve or bushing 33 in turn receives a guide support 34 which is screw-threadedly secured to the sleeve 33 at its outer end for movement therewith. The guide support 34 has its other end bifurcated to provide spaced prong ends 3535 which receive therebetween the cross-over connection 26. A heat shield 36 is mounted adjacent the prongs 35-35 material or parts being conducting metal. The other parts are preferably constructed of molybdenum or tungsten in order to withstand high temperatures which may reach upwardly of 1450 C. when used in the magnetron of the type described generally in the aforementioned copendiug application of Ernest C. Okress. The supporting arrangement for the heating element provides sufficient rigidity to prevent its interference with the cathode cylinder or sleeve 11 and yet permit sufficient flexibility to permit its axial movement relative thereto to allow for expansion and contraction.

Although only a single embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

What is claimed is:

1. A cathode assembly of the indirectly heated type for use in a resonant-cavity magnetron comprising a cylindrical housing of refractory material, a pair of centrally apertured closures, one of said closures being secured to one end of the housing and the other closure being secured to the other end of the housing, a heating filament within said housing between said closures, said filament comprising a reverse helix providing a pair of spaced legs adjacent one closure and a cross-over portion adjacent the other closure, a tubular conductor having an inner end extending into the aperture of one closure and being in contact with one of said legs of the heating filamerit, a rod conductor disposed axially of said tubular conductor, said rod conductor being in contact with the other leg of the heating filament, a bonnet having an open end extending into the aperture of the other closure, a ceramic sleeve slidably mounted in said bonnet, a guide rod having one end fixed to said sleeve and having its other end bifurcated providing spaced prongs, and said prongs receiving the cross-over portion of the filament.

2. A cathode assembly of the indirectly heated type for use in a resonant-cavity magnetron comprising a cylindrical housing of refractory material, a pair of centrally apertured closures, one of said closures being secured to one end of the housing and the other closure being secured to the other end of the housing, a heating filament within said housing between said closures, said filament comprising a reverse helix providing a pair of spaced legs adjacent one closure and a cross-over portion adjacent the other closure, a tubular conductor having an inner end extending into the aperture of one closure and being in contact with one of said legs of the heating filament, a rod conductor disposed axially of said tubular conductor, said rod conductor being in contact with the other leg of the heating filament, a bonnet secured in the central aperture of the other closure, a non-conducting bushing slidably mounted in said bonnet, a guide support having its outer end secured to said bushing and spaced from the closed end of the bonnet and its inner end bifurcated to provide spaced prongs, said prongs receiving the cross-over portion of the.filarnent and an annular plate positioned adjacent said prongs to provide aheat shield for the filament.

3. A cathode assembly of the indirectly heated ,type for use in a resonant-cavity magnetron comprising a cylindrical housing of refractory material a pair of centrally apertured closures, one of said closures being secured to one end of the housing and the other closure being secured to the otherend of the housing, a heating filament Within said housing between said closures, said filament comprising a reverse helix providing a pair of spaced legs adjacent one closure and a cross-over portion adjacent the other closure, atubular conductor having an inner end extendinginto the aperture of one closure, 21 first plate between and secured to said one closure and one leg of said heating filament to bein contact with the tubular conductor, a rod conductor disposed axially of said tubular conductor, a second plate between and secured to said rod conductor and the other leg of said heating filament, a bonnet having aniopen end extending into the aperture of the other closure, a non-conducting bushing slidably mounted in said bonnet, a guide support having its outer end secured .to said bushing and its inner end bifurcated to provide spaced prongs, said prongs receiving the cross-over portion of the filament and an annular plate positioned adjacent said prongs to provide a heat shield for the filament.

4. A device as in claim 1 further characterized by a first annular plate mounted about said bonnet and a second annular plate mounted about the tubular conductor and said plates being positioned adjacent the respective end closures and having lateral flanged extensions providing for heat dissipation.

References Cited in the file of this patent UNITEDSTATES PATENTS Okress i Nov. 14, 1950 

